Someone over at the Straight Dope message boards asks for help identifying a novel set in a post-apocalyptic world reduced to primitivism, where the rulers use technology (lasers) disguised as magic (wand-blasts). Oddly enough, that could describe many books.
All the message-board poster knows is that the book was published around the same time as A Canticle For Leibowitz by Walter Miller, or maybe a bit earlier. And he gives this description:
The novel ... is "set in a post-nuclear holocaust world, in which some of the main characters appear to do miracles or magic, but it turns out they're actually using technology - either rediscovered or reinvented. So we have 'spears' that emit killing beams - actually lasers - etc."
As with many of the other similar incidents where someone remembers vague details but not the name of the story or the author, it turns out to have several possible answers. Possibilities include Roger Zelazny's Lord Of Light, Robert A. Heinlein's Sixth Column, one of Isaac Asimov's Foundation books, Gather, Darkness by Fritz Leiber, Gene Wolfe's Book Of The New Sun and Harry Harrison's Deathworld trilogy. According to one poster, the Leiber and Heinlein books are similar because editor John W. Campbell fed the same idea to both writers, not worrying about there being too much overlap.